Method of uniformly moistening paper and like hygroscopic web material



c. vALLMHDER 3,191,312 METHOD QF UNIFORMLY MOISTENING PAPER AND LIKE June 29, 1965 HYGROSCOPIC WEB MATERIAL Filed April 16. 1962 INVENTORI CLAES ALLANDER ATT'YS BY MW United States Patent O 3,191,312 METHQD F UNIFORMLY MQlSTENING PAPER AND LiKE HYGRSCOPIC WEB MATERIAL Claes Allander, Bromma, Sweden, assigner to Aktiebolaget Svenska Flaktfabrihen, Stockholm, Sweden Filed Apr. 16, 1962, Ser. No. 187,991 Claims priority, application Sweden, Apr. 17, 1961, 3,999/ 61 2 Claims. (Cl. 34-13) The present invention relates to a method for conditioning paper and like hygroscopic web material. In View of the hygroscopic properties of such material, it is necessary to complete the manufacturing process by conditioning in order to bring the moisture ratio into equilibrium with normal storage atmosphere. Special types of paper are, moreover, subjected to such conditioning treatment in view of stability requirements for printing and the like. The conditioning was carried out in several ways, the moisture ratio being determined, for example, by spraying finely distributed water through nozzles onto the web or by blowing steam against the web while at the same time passing the web over cooled rolls. According to another method, the web is passed through a closed space and subjected therein to the eliect of moist air with suitable controlled relative moisture. In the first mentioned cases, diiculties arise in distributing the moisture uniformly, and there is further a great risk of stain formation, particularly for material with a surface susceptible to staining. There is further the risk that a great portion of the moisture which after application was absorbed only by the outer surface layer will be allowed to evaporate before moisture balance could reach to the interior of the web. As a result thereof, the final moisture ratio will be too low. The last mentioned method, it is true, may render a very satisfactory result, but it requires, on the other hand, a treatment time of considerable length, which again necessitates a large and expensive treatment apparatus.

It is the object of this invention to overcome the said drawbacks and to render possible effective and uniform conditioning in a very short time. The invention is characterized in that the web material is advanced in a plurality of back-and-forth passes between a number of rotary cooled rolls, that the web material during its passage about the rolls is pressed against the same by means of one or a plurality of endless felt webs which also are directed about the rolls, and that in the said space a moisture saturated atmosphere is maintained, all of the said steps having the object of imparting to the said web material during its passage over the said cooled rolls as uniform a temperature as possible and a uniformly distributed moisture.

According to a suitable embodiment, the conditioning may be carried out in two or more steps, in that the web material is passed through a treatment chamber divided into sections, and that in the said sections a relative differentiated atmospheric condition is maintained.

The invention will be described more in detail in the following, reference being made to the accompanying drawing showing by Way of example an embodiment of an apparatus adapted for carrying out the said novel method.

In the drawing 1 designates a closed treatment chamber adapted for conditioning web material. The said chamber comprises heat insulated walls, floor and ceiling ice which lie closely adjacent to a plurality of rotary cooled rolls 2 to advance the web material 3 in back-and-forth passes therebetween, so that both surfaces of the web material are alternately in Contact with the cylinder surface of the cooled rolls. The chamber 1 has, of course, limited openings as at 11, to provide entrance and egress of the web 3, while limiting, as far as practicable the entrance of the outside air or egress of conditioned air from the interior of the chamber. During its passage about the cooled rolls, the web is pressed against the same by two endless felt webs 4a and 4b which together with the web material are directed about the cooled rolls and are further guided by a number of guide rolls Sa and 5b. In the treatment chamber, a moisture saturated atmosphere with a suitable temperature adjusted to the material in question is maintained by air conditioning and circulating means 1t). When contacting the said cooled rolls the web material absorbs on the roll surface moisture precipitated from the said atmosphere whichdue to the uniform contact ensured by the said felt websis distributed uniformly in the web material. The hygroscopic felt webs absorb even moisture from the atmosphere, which moisture is also transferred to the web material during its passage over the cooled rolls.

The number of cooled rolls and the length of the felt webs may be adjusted in each individual case to the capacity desired. The shape and construction of the said treatment chamber as well as the location of the cooled rolls and of the guide rolls may, of course, be varied in many ways within the scope of the inventive idea. In certain cases it may be preferable to divide the treatment chamber by partitionsinto a plurality of separate sections through which the web material is caused to pass and wherein relative differentiated atmospheric conditions are maintained.

What I claim is:

1. The method of uniformly moistening a continuous web of paper or similar hygroscopic material, comprising the following steps: providing a closed treatment chamber having disposed therein a plurality of spaced, rotatable, cooled rolls, said treatment chamber having walls lying closely adjacent to said rolls, advancing the web in a number of back-and-forth passes over said rolls, maintaining within said chamber a controlled atmosphere of relatively high humidity and regulated temperature, pressing an endless felt against the web alternately on the exterior of said web as it passes over said rolls, and concurrently therewith maintaining said felt web wholly Within said chamber whereby said web has a relatively uniform moisture condition throughout its extent.

2. The method as set forth in claim 1, which further comprises: treating the web in successive stages in successive treatment chambers, and maintaining different controlled atmospheres in the different chambers.

References Cited bythe Examiner UNITED STATES PATENTS 2,337,163 12/43 Milne 34--116 2,344,686 3/44 Fanselow 34-18 2,661,669 12/53 Friedrich 34-13 3,079,699 6/63 Fry 34-116 FOREIGN PATENTS 564,356 9/ 44 Great Britain.

NORMAN YUDKOFF, Primary Examiner. 

1. THE METHOD OF UNIFORMLY MOISTENING A CONTINUOUS WEB OF PAPER OR SIMILAR HYGROSCOPIC MATERIAL, COMPRISING THE FOLLOWING STEPS; PROVIDING A CLOSED TREATMENT CHAMBER HAVING DISPOSED THEREIN A PLURALITY OF SPACED, ROTATABLE, COOLED ROLLS, SAID TREATMENT CHAMBER HAVING WALLS LYING CLOSELY ADJACENT TO SAID ROLLS, ADVANCING THE WEB IN A NUMBER OF BACK-AND-FORTH PASSES OVER SAID ROLLS, MAINTAINING WITHIN SAID CHAMBER A CONTROLLED ATMOSPHERE OF RELATIVELY HIGH HUMIDITY AND REGULATED TEMPERA- 